Notebook computers, also known as laptop computers, are widely used by persons who require a mobile computer system. Unlike desktop computers, a notebook computer is compact and light, so that it can be easily carried to a meeting or other destinations where computing may be necessary. Furthermore, a notebook computer can operate on a battery, thereby eliminating the need to be constantly connected to an external power supply, i.e., an AC outlet. Although notebook computers are compact, the computational capabilities of notebook computers may be as powerful as their desktop counterparts.
A concern with notebook computers is that a notebook battery typically can last only a few hours. Although advances in battery and circuit designs have increased the operating life of a notebook battery, the mobile use of a notebook computer is still very much limited by the notebook battery life. One way to alleviate this concern is to carry backup batteries. When the power of the installed notebook battery is depleted, the installed notebook battery can be replaced with a fresh backup battery, effectively extending the battery-operated life of the notebook computer. Another way to alleviate the above concern is to carry an AC/DC adapter. The AC/DC adapter can be used to supply external power to the notebook computer and to recharge the installed notebook battery when an AC outlet is available. However, during extended periods when an AC outlet is not available, the only means for continued operation of the notebook computer is utilizing the backup batteries.
Although depleted notebook batteries can be recharged in a separate battery charger, a depleted notebook battery is typically recharged using the notebook computer as a battery charger. This method of recharging a battery using a notebook computer will be described with reference to a conventional power supply configuration 10, which is illustrated in FIG. 1. The conventional power supply configuration utilizes an AC/DC adapter 12 for supplying electrical power to a notebook computer 14 and for recharging an installed notebook battery 16 when it is installed in a battery compartment 18 of the notebook computer. When the AC/DC adapter is connected to an AC outlet, the AC/DC adapter converts the received AC into DC to supply electrical power to the notebook computer. The supplied electrical power is used to provide operating power for the notebook computer. In addition, the supplied electrical power is used to recharge the installed notebook battery.
A disadvantage of the power supply configuration 10 of FIG. 1 is that a backup battery cannot be recharged while the notebook computer 14 is running on the installed battery 16, since the notebook computer can only accommodate a single battery. Another disadvantage is that only one notebook battery can be recharged at a given time. Therefore, in order to recharge multiple notebook batteries, the batteries must be recharged one at a time.
The above-described disadvantages can be alleviated if the notebook computer 14 is a type of notebook computer that includes a slot that can be used for a module drive (e.g., CD-ROM drive or a floppy disk drive) or an extra notebook battery. Using such a notebook computer, it is possible to have two notebook batteries in the notebook computer for recharging. However, the use of the slot for the extra notebook battery is at the expense of the module drive. That is, the user of the notebook computer may not be able to operate a program from a CD or to save a file on a floppy disk when the slot is occupied by the extra notebook battery.
An external battery adapter of interest is described in U.S. Pat. No. 5,200,685 to Sakamoto. The Sakamoto adapter can operate as a battery charger to recharge a notebook battery when the battery adapter is connected to an AC/DC adapter. Alternatively, the Sakamoto adapter can operate as an external power source for a notebook computer when the battery adapter is coupled to the notebook computer, instead of the AC/DC adapter. The adapter of Sakamoto is configured to accommodate a single notebook battery. The Sakamoto adapter allows a backup notebook battery to be recharged while the notebook computer is operating from the installed notebook battery. However, the Sakamoto adapter does not allow multiple notebook batteries to be recharged simultaneously.
Another device of interest is described in U.S. Pat. No. 5,420,493 to Hargadon et al. The device of Hargadon et al. is an integrated device that includes an AC/DC adapter unit and a battery charger unit. The Hargadon et al. device is configured to allow the battery charger unit to be separated from the AC/DC adapter unit. The battery charger unit is structurally configured such that two notebook batteries can be inserted into two accommodating slots of the unit in order to recharge the inserted batteries. Unlike the battery adapter of Sakamoto, the device of Hargadon et al. can simultaneously supply electrical power to a notebook computer and provide charging current to one or two external notebook batteries. The device of Hargadon et al. addresses the above disadvantages related to the conventional power supply configuration 10 of FIG. 1. However, the device of Hargadon et al. is relatively bulky, making it difficult to pack the device in a suitcase when traveling, especially if the device is being used to recharge only a single backup battery. Furthermore, since the slots of the battery charger unit have fixed dimensions, only notebook batteries of one particular size that can be recharged by the battery charger unit of the Hargadon et al. device.
In light of these concerns, what is needed is a compact battery charging device that can recharge more than one notebook battery of different sizes, as well as supply power to a coupled notebook computer, and be of a compact size in order to be easy to pack.